Berry Bling Shines on Forever

Clusters of iridescent marbles must look delicious to some birds, and that’s the secret of success for the fruit of the Pollia condensata plant.

The plant’s berries glisten without any pigment and never fade. Birds are attracted to the shine of the funky fruit although it has no nutritional value. The seeds within the bedazzling berries are then distributed when the feathered art-lovers snatch the berries, possibly to glamorize a nest or attract a mate with some berry bling.

The secret to the plants ever-gleam look is the structure of the cellulose in the berries’ skin. A study published in the Proceedings of the National Academy of Sciences detailed how the brilliant berries create their rainbows and suggested ways to use biomimicry to make eternally iridescent materials.

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“This obscure little plant has hit on a fantastic way of making an irresistible shiny, sparkly, multi-coloured, iridescent signal to every bird in the vicinity, without wasting any of its precious photosynthetic reserves on bird food,” said one of the study’s authors, Beverley Glover of the University of Cambridge, in a press release.

Glover’s team found that specially structured layers of cellulose reflect light off the berries’ skin. Thicker layers of this cellulose reflect red and green while thinner layers shine blue. Unlike pigments, since the shine is produced by the structure of the cellulose it never fades as long as the cellulose structures remain intact. The researchers found that samples of the plant preserved in an herbarium since the 19th century still glistened like new.

“By taking inspiration from nature, it is possible to obtain smart multifunctional materials using sustainable routes with abundant and cheap materials like cellulose,” lead author Silvia Vignolini, of the University of Cambridge, said in a press release. “As an example, edible cellulose-based nanostructures with structural color can be used as substitutes for toxic dyes and colorants in food. Moreover, the fact that the processes involved in cellulose extraction and manipulation are already used in the paper industry facilitates the use of such materials for industrial applications such as security labeling or cosmetics.”

Pollia condensata isn’t nature’s only species to sport iridescent bling. Morpho butterflies, peacocks, and scarab beetles all shine on using similar structures to the berries’ shiny cellulose.

IMAGE: A cluster of fruit from the the Pollia condensata plant. Credit: Silvia Vignolini